diff --git a/update/update.sh b/update/update.sh
index c76130a..44ca8a0 100755
--- a/update/update.sh
+++ b/update/update.sh
@@ -1,10 +1,14 @@
 #!/bin/sh
 
-/bin/echo "Usage: sudo clearpassword=<password> -E update.sh"
+if [[ -z $clearpassword ]]; then
+	/bin/echo "Usage: sudo clearpassword=<password> -E update.sh"
+	exit 1
+fi
+
 password=`/bin/cat /etc/txtpwd`
 auth=`/bin/echo -n $clearpassword | /usr/bin/sha512sum | /usr/bin/cut -d' ' -f 1`                                                             
 
-if [ "$auth" != "$password" ]; then
+if [[ "$auth" != "$password" ]]; then
         /bin/echo "Wrong password"
         exit 1
 fi